Research into whisky maturation

Professor Otto Hermelin of Stockholm University is nearing the halfway point of a 10 year study into what is actually happening in whisky maturation, and how certain conditions in a warehouse affect it.

Otto has about 20 casks in total under observation in four different Islay distilleries; 10 of these are stored in Warehouse 14 at Bruichladdich, on the lowest, middle, and highest racks. There are Bourbon barrels wearing loggers to record humidity and temperature, which correlate with a logger on the outside of the building, all sending their data hourly to Otto, “So I get a really nice curve.”

He is looking for the amount of variation in the different positions. “At the low level, the temperature and humidity doesn’t vary very much. Compared to what it does high up, where you have a temperature variation of, say, 6 degrees and up to 24 degrees during the summer months. There the casks are working much more, they are much more active compared to when you put them at a low level. That will certainly make the maturation process different in the different places.”

Otto’s background is in micro-paleoantology (fossils). He first came around the Islay distilleries thanks to a geology field-trip, and having noticed the copper sulphate deposits in the spirit safe, became interested in working out why 10 year old whisky contained so little copper compared to new-make. “And I started to read about it and found out that I couldn’t find anyone that had learnt how the maturation process goes on. I mean, they had examined new-make spirit, 5 year old, 10 year old, 15 year old, but not on the same new-make. That’s when I thought, “OK, we will try to do that” and we had all the equipment back home in Stockholm. Then I approached all the distilleries on Islay and four of them said yes, the other ones said, ‘it’s our secret’.”

Twice yearly for five years now, he has analysed physical samples from the casks with gas chromatography, so as to map “organic chemistry and the inorganic chemistry, pH and things like that, esters, the alcohol content, so it will be a complete list of what’s in there, actually.”

He plans to take plugs from the same staves of the casks too, ten years apart, to explore how much the wood is taking up of different metals, for instance, copper. “Then you also have things that are moving back and forth through the cask like sodium, things like that, that goes in from the sea water. Because you don’t have that in the casks from the beginning.”

In spite of his powerfully academic approach, he admits that maturation is, “much more fun when it’s sort of natural.” With the advent of climate-controlled warehousing, however, particularly in the United States, he notes that, “if you know what is happening in different climate, temperature, different humidity, then you can specify, ‘I would like to have this type of whisky’. And you can store it in that environment, then you can get it. In theory, you can get it.”

“I hope that this project will show when different esters are developing. Different things that you taste when they develop in the cask. It’s not always better to store it for a longer time, because you lose some other things. If you are looking for something special, OK, it’s enough with 5 years, it doesn’t get any better to have it 15 years or so. We’ll see. We’ll see.”

Otto’s report on his findings at five years into the study is to follow later on this year.